1. Field of the Invention
The invention relates generally to semiconductor devices, and more particularly to a novel Metal Insulator Metal (MIM) capacitor and method for creation of the same.
2. Description of the Related Art
Metal Insulator Metal (MIM) capacitors are important because chip miniaturization requires integration of multiple passive components. Capacitors are just one such passive device. Advantages of a MIM capacitor include decreased footprint, higher quality factor, and lower parasitics. A MIM capacitor comprises an insulator, which separates two metal layers. One disadvantage associated with prior art MIM capacitors are edge defects that occur in the insulator at the interface with the top metal layer.
FIG. 1 depicts a prior art MIM capacitor 100 which is prone to edge defects. Edge defects result in early device failure. Therefore, to improve yield it is desirable to eliminate edge defects or weak dielectric at the periphery of the top electrode from the top electrode etching in a MIM capacitor. An insulator 104 separates two conductive layers 102. Edge defects 110 occur in the insulator 104 at the interface of the insulator 104 with the top conductive layer 102. In an effort to obviate edge defects, a pullback chemistry was developed. Such pullback chemistry results in a MIM capacitor with an insulator 104 that is thicker at the interface with the top conductive layer 102. FIG. 2 depicts a prior art MIM capacitor with pullback.
FIG. 2 depicts a prior art MIM capacitor with pullback 200. The pullback chemistry results in a MIM capacitor 200 with a top conductive layer 102 that is pulled back 220 at the interface of the conductive layer 102 with the insulator 104. The insulator 104 is thicker 230 at the interface with the top conductive layer 102. The thickened insulator 104 reduces edge defects and also reduces leakage. Leakage reduction improves yield. One disadvantage of a MIM capacitor with pullback 200, however is that such construction only works with an insulator 104 comprised of low-K dielectric, e.g. SiN. Such construction, however, does not work with an insulator 104 comprised of high-K dielectric. As one skilled in the art would recognize, high-K dielectric includes, but is not limited to the following materials: Ta2O5, Al2O3, and HfO2.
FIG. 3 depicts a prior art MIM capacitor with pullback with an insulator comprised of high-K dielectric 300. The insulator 104′ comprises high-K dielectric. The pullback chemistry results in not only a MIM capacitor with a top conductive layer 102 that is pulled back 220 at the interface of the conductive layer 102 with the insulator 104, but also a MIM capacitor with a thin insulator 104′ at the interface. Such insulator 104 results in edge defects and increased leakage.
What is needed in the art is an improved MIM capacitor that reduces edge defects and maintains high yield for all dielectrics.